Aerodynamically adjustable pantograph

ABSTRACT

Apparatus for maintaining a substantially constant force between a pantograph collector shoe and an overhead contact wire by aerodynamically moving the shoe to follow the vertical profile of the contact wire. The position of the contact wire is detected with respect to the collector shoe or its supporting frame and an airfoil attached to the pantograph is adjusted in response thereto to provide the requisite amount of positive or negative aerodynamic lift for the shoe to adjust its vertical position in correspondence with that of the overhead contact wire.

United States Patent 1191 Gray 7 1111' 3,823,278 1451 July 9, 1974AERODYNAMICALLY ADJUSTABLE PANTOGRAPH [75] Inventor: Richard T. Gray,Erie, Pa.

[73] Assignee: General Electric Company, Erie, Pa. [22] Filed: Dec. 26,1972 [21] Appl. No.: 318,182

[52] U.S. Cl 191/66, 191/45, 191/65 [51] Int. Cl B601 5/12 [58] Field ofSearch 191/45, 47, 48, 49, 50,

[56] References Cited UNITED STATES PATENTS 2,996,267 8/1961 Warren244/75 A 3,238,314 3/1966 Faivelbyf. 191/66 FOREIGN PATENTS ORAPPLICATIONS 1,074,622 2/1960 Germany 191/66 Primary Examiner-M. HensonWood, Jr.

Assistant Examiner-D. W. Keen Attorney, Agent, or FirmWalter G. Bemkopf;Dana F.Bigelow [57] ABSTRACT Apparatus for maintaining a substantiallyconstant force between a pantograph collector shoe and an overheadcontact wire by aerodynamically moving the shoe to follow the verticalprofile of the contact wire. The position of the contact wire isdetected with respect to the collector shoe or its supporting frame andan airfoil attached to the pantograph is adjusted in responsethereto toprovide the requisite amount of positive or negative aerodynamic liftfor the shoe to adjust its vertical position in correspondence with thatof the overhead contact wire.

f 12 Claims, 14 Drawing Figures PATENTEDJUL 91w 3.823.278

SKEU 1 BF 6 PR/OR ART PATENTED 91914 3.823.278 SHEET 2 F 6 m mi 2. M a

PATENIEuJuL 9mm 3,823,278

SHEET 3 OF 6 FIG. 6 32 Pmimmm slam sum 6 or 6 AERODYNAMICALLY ADJUSTABLEPANTOGRAPH This invention relates generally to pantograph structures andmore particularly to mechanisms for adjusting the vertical positionthereof to accommodate a contact wire having a variable verticalprofile.

Conventional pantographs of the type used for the high speed pickup ofpower from an overhead cantenary comprise at least two elasticsuspensions; the springs which balance the weight of the frame, and thesprings which suspend resiliently the comparatively low inertia powerpickup element on the collector shoe. The frame, which is necessarily ofconsiderable weight, moves vertically in response to high amplitude andlow frequency variations in the height of the contact wire with respectto the vehicle. Poor response is thus obtained from pressure variationsbetween the shoe and the contact wire. These pressure variations may bebrought about by variation in the height of the contact wire above thetruck, variation in the nature of the supporting system for the contactwire, and variation in loading on the current collector brought about,for example, by variation of the wind pressure as the speed ofthe'vehicle changes or by icing.

The collector shoe which is adapted to maintain frictional contact withthe overhead wire is made as light as possible so that it can readilymove in response to small amplitude high frequency variations in theheight of the contactor wire with relation to the vehicle. However,since the collector shoe supporting springs have a limited elasticrange, their effect is removed from the mechanism during periods inwhich greater variations exist.

In combination, the stiff support offered by the frame springs, and thesoft support given by the shoe springs provide an upward force, commonlycalled the push up force which presumably maintains a uniform forcebetween the-shoe and the overhead wire. However, because of the degreeof variations and the nature of the supporting springs the response isinadequate to provide such a uniform force.

In recognition of the problem, various devices have been. fabricated inwhich supplementary apparatus is utilized to vary the height of the shoeor the frame in response to the pressure variationsmentioned hereinabove. The pressure variations are measured either directly, such as bypiezoelectric methods, or indirectly by measurement of displacementvalues. Translation of the measurements is then applied to some form ofelevating device to raise or lower the collector shoe in responsethereto. The elevating device is conventionally powered byservocontrolled devices of thepneumatic, hydraulic or'electrical type.Provision of this auxiliary power is costly and difficult to obtain. Forexample, in

frameor to the contactor shoe. Aerodynamic lift is thus provided theretoas the pantograph travels along the rail. This lift, however, variesonly in relation to vehicle speed and does not accommodate theaforementioned pressure variations. Further, the apparatus does notselectively provide for either positive or negative lift nor, in somecases, for operation in either direction of vehicle travel.

It is therefore an object of this invention to provide an improvedapparatus for controlling the vertical motion of a pantograph inrelation to the force between the collector shoe and the overhead wire.

Another object of this invention is the provision for controlling thevertical position of a pantograph without the use of an external powersource.

Yet another object of this invention is the provision for a controlledpantograph which operates equally well in either direction of vehicletravel.

Still another object of this invention is the provision in a controlledpantograph without an external power source, for moving the pantographdown when the shoe/wire interface force increases and up when that forcedecreases.

These objects and other features andadvantages become more readilyapparent upon reference to the following description when taken inconjunction with the appended drawings.

SUMMARYOF THE INVENTION Briefly, in accordance with one aspect of theinvention an airfoil element is attached to either the collector shoe orthe pantograph frame to provide aerodynamic lift thereto in relation tothe speed at which the vehicle and mounted pantograph are travelingalong an hydraulic control system a fluid at high pressure must beconstantly delivered to the pantograph frame. Besides the requirementfor considerable horsepower to deliver the fluid, additional problemsare encountered since the pantograph frame is charged to the same highelectrical potential'as the overhead contact wire. Clearly it isdesirable to have a supplementary system to control the pantographheight, but the power requirement may not justify the advantages gainedby use thereof.

Various types of elevating means have been devised wherein wind vanesare secured to the pantograph the contact wire. A feedback deviceadjusts the attitude of the airfoil in response to the interactive forcebetween the collector shoe and the overhead contact wire so as toprovide to the shoe an appropriate aerodynamic lift over a range ofpositive and negative values to maintain a substantially constantcontacting force with the contact wire. The apparatus which raises andlowers thepantograph is powered entirely by the air currentsinteractingwith the pantograph and associated airfoil, and provision is made forits effective usage regardless of the direction in which the vehicle istraveling.

BRIEF DESCRIPTION OF THE DRAWINGS collector shoe.

FIG. 3 is a sectional view of the collector shoe and airfoil portions ofthe preferred embodiment.

FIGS. 4, 5 and 6 are sectional views of modified embodiments of theairfoil portion thereof.

FIG. 7 is a modified embodiment of the invention.

FIGS. 8 and 9 show another embodiment of the invention as applied to thepantograph frame.

FIGS. 10 and 11 illustrate a type of sensing and adjusting meansutilized with the structure of FIGS. 8 and 9.

FIG. 12 is a modified embodiment thereof.

FIG. 13 illustrates another type of sensing and adjusting means utilizedwith the structure of FIGS. 8 and 9.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is now made to FIG. 1wherein a portion of an electrical propulsion vehicle 11 has mountedthereon, through insulators 12, a pantograph 13 of the conventionaltype. The pantograph 13 comprises a base 14; a frame having lower arms16 pivotably attached thereto, and upper arms 17 connected at theirupper ends by a joint 18; and a collector element 19 extending upwardlyfrom the joint 18 to contact an overhead wire (not shown). A pair oftension springs 21 are attached, one to each of the frame lower arms 16,to bias them inwardly towards each other so as to cause the joint 18 andthe attached collector shoe 19 to be biased upwardly. Crank arms rigidlyattached to the respective lower ends of the lower arms 16 and connectedby a common link tend to maintain the diamond configuration.

The collector element 19 is typically mounted at the joint 18 by a shaft22 slidably disposed in a cylindrical casing 23 and biased upwardlytherein by a compression spring 24. A casing stem 26 having the ends ofpivotal links 27 slidably attached thereto maintains the casing 23 andassociated shaft 22 in a constant vertical position.

The combination of the two tension springs 21 biasing the frame upwardlyand the compression spring 24 urging the collector element 19 upwardlywith respect tothe frame, is designed to push against the contact wirewith a substantially constant force commonly referred to as thepush-up-force. However, for reasons discussed hereinbefore, the reactionof the springs alone is inadequate to provide a uniform contact forcebetween the collector element 19 and an overhead wire having a variabledisposition.

Referring now to FIG. 2, one concept of the improved pantograph isillustrated. A portion of the collector element '19 is shown with a pairof collector shoes 28 and 29 having wear strips 31 and 32, respectively,forfrictional contact with the overhead wire 33. Extending oppositelyfrom the shoes 28 and 29 along the line of travel are airfoil elements34 and 36 respectively, whose structure and function will be more fullydescribed hereinafter.

Also attached to the shoes 28 and 29, and extending oppositely along theline of travel, are support arms 37 and 38, respectively. The rigidcombinationof collector element 19, the symmetrically disposed collectorshoes 28 and 29, and the arms 37 and 38, provide a balanced structurewhich is free to move vertically as heretofore explained. The supportarms 37 and 38 have for their purpose the supporting of sensingmechanisms 39 and 41.

It should be noted that various types of sensing mechanisms may beutilized as, for example, photo-electric means or electro-magneticmeans. The function, however, is the same in any case; the detection ofheight variation in the contact wire 33 at a point forward of thecollector shoes in the direction of vehicle travel.

The illustrated mechanical sensing mechanisms 39 and 41 are identicaland are designed for use, one at a time, in either direction of vehicletravel, with the leading mechanism in operation and the trailing one inan ineffective condition. The following description of the mechanism 41can be applied as well to the mechanism 39 as to that mechanism 41. Itcomprises a sensor arm 42 having attached at its one end a'sensor 43 formaintaining frictional contact with the overhead wire 33, and a link i44, pivotally interconnecting the support arm 38 and the sensor arm 42.A signal arm 46, also interconnecting the support arm and the sensorarm, provides for a fourbar linkage so as to maintain the sensor arm 42in a vertical disposition and ensure that the sensor 43 does not rotate.A linkage spring 47 is provided to support the dead weight of the sensor43 and keep it against the wire when the vehicle is at rest or movingslowly. The sensor 43 preferably includes a thin wear strip 48 attachedto the top of a wedge which acts like an airfoil to hold the wear stripup against the overhead wire.

The signal arm 46, which is pivotable on the support arm 38, is linkedat its rearward end 49 to a rocker arm 51 rotatably mounted to thecontactor shoe 29. Rotation of the rocker arm 51 on its axis 52transmits motion to an actuator lever 53 which in turn brings about theshoe configuration causes a change in its aerody- I namic character andresults in a positive or negative lift thereto, to move the wear strip32 toward or away from the overhead wire 33. The opposite rocker arm 55operates simultaneously with the rocker arm 51 to similarly adjust itsassociated airfoil element 34. However, in this design, only the airfoilelement of the leading collector shoe will be aerodynamically effective.

Operation of the apparatus is as follows when the vehicle is moving fromleft to right. If the contact wire ahead of the moving shoe 29 is lowerthan the shoe, excessive force will build up between the shoe and thewire absent the apparatus. But with the subject apparatus, the sensor 43is pushed down rotating the signal arm 46 and in turn the rocker arm 51,clockwise. This causes the airfoil element 36 to be further extendedfrom the shoe29 and the aerodynamic force to push down on the shoe, thusreducing the excessive force between the shoe and the overhead wire.Conversely, if the wire ahead of the moving shoe is higher than at theshoe, the linkage spring 47 and the aerodynamic lift on the sensor picksit up, rotating the signal arm and rocker arm clockwise. The airfoilelement 36 is retracted and a second airfoil element (not shown), lo'cated at apoint on the upper portion of the shoe, is extended so as tochange the aerodynamic lift to a positive value. As a result the shoe ispushed up so that it can follow the rising overhead wire and maintaincontact'therewith. The trailing sensing device 39 just follows along inan inoperative condition since its airfoil elements are out of the airstream and thus rendered ineffective. However, when the vehicle isreversed, the sensing mechanism 39 then leads and becomes operative in amanner just described and the mechanism 41 becomes the inoperativetrailing mechanism. The apparatus thus works equally well in eitherdirection of travel.

In the arrangement shown at FIG. 2, it is possible that there will beinsufficient force available at the rocker arm to move the actuatorlevers under each shoe element, or, if there is sufficient force, theinterface force between the sensor and the overhead wire will be so highas to cause excessive wear of the wear strip 48 and to lift the wireahead of the shoe. This would present an undesirable false signal backto the main shoe. Thus, it may be necessary to give the sensor moreleverage by increasing the length a and reducing the length b. Anotheralternative is to utilize the signal arm 46 to operate an air valvewhich would control booster air cylinders 50. If the external powerboost is necessary, it can be obtained from the vehicle air supplythrough an insulated tubing arrangement. It would only require afraction of the power to control aerodynamic lift that it requires todrive the entire pantograph frame directly as is done in the prior art.An alternate arrangement of FIG. 2 would be to attach the support arms37 and 38 to the cylindrical casing 23 as in another embodiment of thisinvention shown by FIG. 14. In FIG. 2 this alternate attachment wouldrequire that length a be increased and length b decreased because thesensors 43 would then undergo relatively larger displacements.

Construction of one embodiment of the contactor shoe 29 can be betterunderstood by reference to FIG. 3. A frame 54 has secured thereto byscrews 56 the wear strips 32. Also attached to the frame 54 is a casing57 which is held in place by a plurality of screws such as screw 58.Formed in the casing 58 at one end thereof are upper and lowerapertures, 59 and 61 respectively, in which the airfoil elements areslidably disposed and adapted to protrude therefrom. The lower airfoilelement 36 is disposed between the lower wall of the casing 57 and aparallel guide tab 62, and has a pair of normally projecting ribs 63defining a notch in which a crankarm post 64 is fitted. The crank 66 ismounted on a shaft 67 and is caused to rotate by movement of theactuator lever 53 which extends downwardly through a casing slot 68. Theopposite crankarm post 69 similarly fits between ribs 71 of an upperairfoil element 72 which is disposed in the aperture 59 and verticallysupported by upper and lower guide tabs 73 and 74, respectively.Movement of the actuator lever brought about by rotation of the rockerarm 51 (FIG. 2) causes rotation of the crank 66 which moves the airfoilelement 36 and 72 in and out of the apertures to change the aerodynamiccharacteristics of the shoe 29. The po-- Various modified embodiments ofthe shoe configu-- ration are shown in FIGS. 4, 5 and 6, all of whichhave for their design purpose the provision for selectively changing theaerodynamic characteristics of the shoe.

The design shown in FIG. 4 is similar to that of FIG. 3

in that it has a lower lip 36 which protrudes by an amount determined bythe degree of lift desired. Instead of a crank, a fourbar-linkagearrangement is utilized with parallel links 76 and 77, pivot posts 78and 79, and connecting posts 81 and 82.

The design of FIG. 5 utilizes a back surface 83 hinged at the lower edgesuch that the trailing element has increasing aerodynamic lift as theback is further opened. With such a design the leading element is notaffected by the manipulation of its back surface.

In FIG. 6 a design is shown wherein a concave airfoil 86 is exposed inthe direction of travel with its attitude being controlled by afour-bar-linkage 87. In the position shown a positive aerodynamic liftwould result; however, a rotation of the four-barlinkage in the clockwise direction would bring about a negative aerodynamic lift.

Various other designs and combinations of those designs heretoforedescribed may be utilized to effect a change in shoe configuration ascontemplated by this invention.

The embodiment shown in FIG. 2 senses vertical variations in theoverhead wire position with respect to the contactor shoe 29. Variousother sensing and actuating schemes may be utilized, such as sensing thedisplacement of the contactor shoes with respect to the pantograph frameas it varies in relation to the force of the overhead wire on the shoewear strips. One type of mechanism to accommodate this function is shownin FIG. 7. The design is similar to that of FIG. 2 in that a pair ofcontactor shoes 28 and 29 are rigidly connected to the collector element19, and each has a rocker arm 51 to move the actuator lever 53 byrotation of the rocker arm about its axis 52. The collector element 19of its shaft 22 are, however, sprung from the casing 23 in a mannersimilar to that shown in FIG. 1. As the force between the overhead wireand the contactor shoes 28 and 29 varies the collector element and shoeswill accordingly move vertically with respect to the casing 23 whichforms part of the pantograph frame. It is this movement which causesadjustments to be made in the position of the airfoils 34 and 36 andthereby bring about vertical movement of the shoes to correspond withthat of the overhead wire position.

Rigidly secured to the casing 23 is a mounting plate 88 having pivots 89and 91 thereon. Rotatably secured to the pivots 89 and 91 are the endsof pivot links 92 and 93 whose opposite ends are pivotably linked torocker arms 55 and 51, respectively.

In operation, when the leading shoe 29 is pushed downward against thespring suspension of the collector element 19 by an excessive force fromthe overhead wire, the vertical distance between the shoe and thepantograph frame (the casing 23) is shortened. The link 93 pushes up onthe rocker arm 51 rotating it clockwise and actuating the negative liftconfiguration as shown. A downward aerodynamic force would be applied tothe shoe 29 to relieve the high interface force between the overheadwire and the shoe. Conversely, as the force on the shoe decreases belowthe desired value, the spring suspension pushes upward with respect tothe frame, and the positive aerodynamic lift configuration is actuatedto raise the shoe forward to the overhead wire. It should be noted thatthe airfoil element 34 and 36 are adjusted simultaneously with only theleading element being aerodynamically effective, regardless of thedirection of travel.

In the mechanisms thus far described, airfoil elements have beenattached directly to the collector shoes to change the vertical positionthereof. An alternative arrangement which is shown in FIG. 8 and 9utilizes an airfoil element 94 secured directly to the pantograph framecasing 23 on an axis 96 transverse to the direction of travel. Anairfoil element similar to that shown in FIG. 9 is secured to the otherside of the pantograph frame and operates in unison with the airfoilelement 94. Together, the two airfoils act to raise or lower the entirepantograph frame in either direction of vehicle travel, with the degreeof lift being determined by the attitude of the airfoils with respect tothe axis 96. A flap 97 is mounted above (or below) the airfoil 94 forthe purpose of meeting the bi-directional travel requirement. Forexample, if the vehicle is moving from left to right, the air pressureon the flap tends to rotate the entire airfoil 94 counterclockwise andthereby provide a positive angle of attack (upward force). After thisinitial orientation, the airfoil may be controlled to produce varyingdegrees of positive and negative lift forces as will be describedhereinafter. A light spring 98 is preferably installed to maintain theairfoil in substantially a neutral position when the vehicle is at restor moving slowly.

Illustrated in FIGS. 10 and 11 is one method of controlling the airfoils94 by using the relative displacement between the shoe 29 and the framecasing 23. Attached to the bottom of the shoes and depending therefromare a pair of struts 99 (only one shown) interconnected at their lowerends by a central shaft 101 aligned transverse to the direction oftravel. The shaft is supported by bearings 102 at the struts and has oneach of its ends a crankarm 103. Attached to the end of each of thecrankarms 103 are a pair of flexible links 104 and 106 such as cords orchains. The opposite ends of 'the flexible links are attached to theairfoil 94 at the connection point 105. The length of the links 104 and106 are such that they are almost slack when the shoe is not touchingthe overhead wire (i.e., when the shoe is at the maximum vertical heightwith respect'to the frame). When the shoe is held up against the wirewith just the static push-up force, the links will then be slack. Withlittle or no motion of the vehicle the crankarms 103 will be in thedownward vertical position. The light spring 98 and crankarmcounterweights would further assure this.

Also attached to the bottom of the shaft 101 is a central flap 107. Thisflap is utilized to orient the shaft 101 and crankarms 103 so as torender effective the proper link, 104 or 106, in accordance with thedirection of travel. For example, as the vehicle beings to move fromleft to right in FIG. 10, the shaft 101 is rotated clockwise by theforce of the air on the central flap 107. When it reaches the horizontalposition shown, the crankarms 103 will impinge on their stops 108 at theleft with the link 104 being in a slackened condition and the link 106being pulled taut by the crankarm 103. As the interface force betweenthe overhead wire and the shoe increases excessively, the shoe with itsattached shaft 101 and crankarms 103, is pushed downward against itssupport springs. The link 106 pulls down on the leading edge of theairfoil 94 to cause the aerodynamic lift thereof to move towards a morenegative value. It should be noted that the airfoil flap 97 keeps thelink 106 taut, and, due to the position of the crankarm stop 108, .theposition of the crankarms 103 are fixed for that direction of travel.The central flap 107 merely positions the crank initially to its correctoperating position for the particular direction of vehicle travel.

As the interface force between the overhead wire and the shoe decreasesexcessively, the shoe is raised up by its support springs, and thecrankarms 103 raise with respect to the casing 23, thereby allowing theairfoil 94 to be rotated counterclockwise by the flap 97 or a morepositive angle of attack. This causes an upward force on the airfoil 94to raise the frame casing 23 and the shoes upward toward the wire.

When the train stops the central flap 107 and crankarms 103 return tothe vertical position and the link 106 is nearly slack. If the vehiclethen moves in the opposite direction (right to left), the shaft isrotated counterclockwise so as to bring the crankarms 103 up against thestops 109 on the right side. The link 106 is thus slackened, and thelink 104 is pulled taut to control the airfoil in that direction oftravel.

A variation of the embodiment just described is shown in FIG. 12,wherein the airfoil flap 97 is attached below the airfoil and thecentral flap 107 is attached above the shaft-101. The crankarm stops 108and 109 are then positioned below the crankarms 103 instead of abovethem. The crankarms are counterweighted and a light spring is attachedto assure that the central flap 107 is vertical when the vehicle is atrest.

In operation, as the vehicle moves from left to right, the central flap107 rotates the shaft counterclockwise until the crankarms 103 contactthe stop 108. The link 106 is pulled taut and becomes the controllinglink for that direction of travel in a manner 'similar to that describedfor the design of FIG. 10.

FIGS. 13 and 14 illustrate a modified embodiment, which combines thesensing mechanism of FIG. 2 with the aerodynamic arrangement of FIG. 8.The sensing mechanism comprises the sensor 43 supported by the sensorarm 42 in the center and by sensor arms 11 1 and 112 (not shown) on thesides. The sensor arm 42 is linked to the support arm 38 as shown inFIG. 14 and the sensor arms 111 and 112 are linked to similar supportarms 113 and 114 (not shown), respectively. The

' support arms 1 13 and 114 are mounted directly to their respectivepantograph frame casings 23 as shown in FIG. 13 whereas the centralsupport arm 38 is I mounted, as for example by welding, to a carriershaft 1'16 extending between the opposite casings 23. The carrier shaft116 does not itself rotate but has a bearing 117 on each end thereof andattached to the upper arms of the pantograph which do rotate.

Also attached to the carrier shaft 116 by a pair of brackets 118 is ashaft 119 having rigidly attached thereto at a central point thereon, adouble crankarm 121 with arms extending downwardly and having a middleflap 122 projecting upwardly at equal angles therebetween. The shaft 119is rotatable in bearings 123 and has secured to each end a doublecrankarm 124 similar to the crankarm 121 but having no flap. The doublecrankarm 121 is adapted to be positioned by the wind resistance on themiddle flap 122 so as to engage the appropriate signal arm 46 or 126 asshown in FIG. 14. The crankarms 124, which are rotated in I unison withthe crankarm 121, are each adapted to engage, with either of its pegs127or 128, a lever arm 129 projecting upwardly from its associatedairfoil 94.

In operation, when the vehicle is at rest, the middle' flap 122protrudes upward vertically and the arms of both the double crankarm 121and the double crankarms 124 hang on either side atequal angles with thehorizontal. Neither of the signal arms 46 nor 126 are contacting thecrank 121 and the airfoils 124 are held in the neutral (horizontal)position by a light spring. As the vehicle moves from left to right, theforce of the arm on the middle flap 122 rotates the shaft 119 andcrankarms counterclockwise as shown in FIG. 14. On each side of thepantograph the peg 127 on the crankarm 124 contacts the lever arm 129 ofthe airfoil 94 and the airfoil flap 97 (FIG. 13) tends to rotate theairfoil counterclockwise so as to maintain a positive angle bias. At thesame time, the centrally located crankarm 121 is rotated in unison withcrankarm 124 so that its forward arm contacts the signal arm 46. Thesignal arm 46 then controls its position in response to the verticalposition of the overhead wire in a manner similar to that as describedin FIG. 2. For example, if the vertical position of the overhead wirestarts to go lower than that at the shoe, the sensor 43 is pusheddownward, the signal arm rotates clockwise, and the crankarrn 122 ismoved counterclockwise. The shaft 119 and attached crankarms 124 arealso rotated counterclockwise to change the attitude of the airfoil 94to a more negative attack angle. The aerodynamic force then pushes downon the airfoils 94 and the frame to relieve the buildup of interfaceforce between the shoe and the overhead wire. Conversely, if thevertical position of the overhead wire at the sensor starts to go higherthan at the shoe the sensor 43 raises itself up against the wire and thesignal arm 46 is rotated counterclockwise. This allows the airfoils 94to be rotated counterclockwise by their flaps 97, and the angle ofattack to be increased. The aerodynamic force raises the pantographframe to maintain the proper contact force between the shoe and overheadwire.

As set forth in the description of FIG. 2, this mechanism may notprovide sufficient force at the end of the signal arm 46 to activate theairfoils. Accordingly, it may be necessary to have the signal armoperate an air valve which controls vehicle air pressure to a cylinderwhich in turn activates the airfoils. The middle flap 122 i would thenbe used to switch the air between two cylin-v ders, depending on thedirection of travel.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An improved pantograph arrangement of the type having a collectorshoe resiliently supported on a frame to maintain frictional contactwith an overhead wire, wherein the improvement comprises:

a. at least one airfoil element secured to the pantograph and beingadjustable to provide aerodynamic lift thereto throughout a range ofpositive and negative values as the pantograph travels at various speedsalong the wire in a given direction;

b. means for sensing the force between the collecting shoe and theoverhead wire; and

l c. means for adjusting without supplementary power means said airfoilelement in response to said sensing means to move the collecting shoedown when the force from the overhead wire increases and up when thatforce decreasesso as to maintain a substantially constant force betweenthe collector shoe and the overhead wire.

2. A pantograph arrangement as set forth in claim 1 wherein said sensingmeans comprises a mechanical linkage between the collecting shoe and theframe and further wherein the displacement of the shoe with respect tothe frame is indicative of the pressure between the shoe and theoverhead wire.

3. A pantograph arrangement as set forth in claim 1 wherein said atleast one airfoil element is secured to said collector shoe and is soconstructed as to alter the shoe configuration but not tip the shoe fromits longitudinal plane when acted on by said adjusting means.

4. A pantograph arrangement as set forth in claim 3 wherein said atleast one airfoil element comprises a rigid member extending from saidshoe in the direction 5. A pantograph arrangement as set forth in claim4 wherein said at least one airfoil element comprises a pair ofhorizontal spaced lips slidably disposed in said collector shoe withtheir adjacent ends extendable at one end, one at a time, from said shoeand at their other end connected to said adjusting means, the upper ofsaid lips tending to cause an upward aerodynamic lift on said shoe whenit is extended and the lower of said lip tending to cause a downwardaerodynamic lift thereon when it is extended.

6. A pantograph arrangement as set forth in claim 1 wherein said sensingmeans comprises:

a. a support arm secured to and extending from said collector shoe inthe direction of vehicle travel,

b. a sensor element adjustably secured to said sup port arm at a pointdisplaced from said collector shoe, and extendingupwardly to impinge onsaid contactor wire;

c. biasing means for urging said upward end to maintain frictionalcontact with said contactor wire but allow said sensor element to movewith respect to said arm in response to change in the vertical profileof the contactor wire as the pantograph travels therealong, and

d. detecting means responsive to the movement of said sensor elementwith respect to said support arm to activate said adjusting means.

7. A pantograph arrangement as set forth in claim 1 wherein said atleast one airfoil element is secured to said frame and, further, whereinsaid frame moves up and down with the collecting shoe when said airfoilelement is adjusted in response to said sensing means.

8. A pantograph arrangement as set forth in claim 7 wherein said airfoilelement comprises a wing symmetrically mounted on an axis transverse tothe direction of travel, said wing being pivotable on said axis toselecof travel and secured in such a manner as to have the degree ofextension determined. by said adjusting means.

tively provide negative and positive aerodynamic lift in either of twoopposite directions of travel.

9. A pantograph arrangement as set forth in claim 8 wherein said wingincludes a biasing flap attached to one side thereof and extendingsubstantially normally therefrom, whereby as the pantograph travels ineither of said two .opposite directions, said biasing flap tends topivot said airfoil element or its axis in a direction such that itsleading edge is biased towards the side of the airfoil element to whichsaid biasing flap is attached.

10. A pantograph arrangement as set forth in claim 9 wherein saidadjusting means includes a control flap pivotally attached to saidpantograph on an axis transverse to the direction of travel, saidcontrol flap being larger in cross section than said biasing flap andlinked to said airfoil element in such a manner as to apply a torquethereto opposing that exerted by said biasing flap.

11. A pantograph arrangement as set forth in claim 7 wherein saidsensing means comprises a mechanical linkage between the collecting shoeand the frame and further wherein the displacement of the shoe withrespect to the frame is indicative of the pressure between the shoe andthe overhead wire.

12. A pantograph arrangement as set forth in claim 7 wherein saidsensing means comprises:

a. a support means secured to and extending from the pantograph frame inthe direction of vehicle travel;

b. sensor element adjustably secured to said support in response tochange in the vertical profile of the arm at a point displaced from saidcollector shoe contactor wire as the pantograph travels thereandextending upwardly to impinge on said contacalong; and tor wire; (1.detecting means responsive to the movement of c. biasing means forurging said upward end to mainsaid sensor element with respect tosupport arm to tain frictional contact'with said contactor wire butactivate said adjusting means.

allow said sensor to move with respect to said arm

1. An improved pantograph arrangement of the type having a collectorshoe resiliently supported on a frame to maintain frictional contactwith an overhead wire, wherein the improvement comprises: a. at leastone airfoil element secured to the pantograph and being adjustable toprovide aerodynamic lift thereto throughout a range of positive andnegative values as the pantograph travels at various speeds along thewire in a given direction; b. means for sensing the force between thecollecting shoe and the overhead wire; and c. means for adjustingwithout supplementary power means said airfoil element in response tosaid sensing means to move the collecting shoe down when the force fromthe overhead wire increases and up when that force decreases so as tomaintain a substantially constant force between the collector shoe andthe overhead wire.
 2. A pantograph arrangement as set forth in claim 1wherein said sensing means comprises a mechanical linkage between thecollecting shoe and the frame and further wherein the displacement ofthe shoe with respect to the frame is indicative of the pressure betweenthe shoe and the overhead wire.
 3. A pantograph arrangement as set forthin claim 1 wherein said at least one airfoil element is secured to saidcollector shoe and is so constructed as to alter the shoe configurationbut not tip the shoe from its longitudinal plane when acted on by saidadjusting means.
 4. A pantograph arrangement as set forth in claim 3wherein said at least one airfoil element comprises a rigid memberextending from said shoe in the direction of travel and secured in sucha manner as to have the degree of extension determined by said adjustingmeans.
 5. A pantograph arrAngement as set forth in claim 4 wherein saidat least one airfoil element comprises a pair of horizontal spaced lipsslidably disposed in said collector shoe with their adjacent endsextendable at one end, one at a time, from said shoe and at their otherend connected to said adjusting means, the upper of said lips tending tocause an upward aerodynamic lift on said shoe when it is extended andthe lower of said lip tending to cause a downward aerodynamic liftthereon when it is extended.
 6. A pantograph arrangement as set forth inclaim 1 wherein said sensing means comprises: a. a support arm securedto and extending from said collector shoe in the direction of vehicletravel, b. a sensor element adjustably secured to said support arm at apoint displaced from said collector shoe, and extending upwardly toimpinge on said contactor wire; c. biasing means for urging said upwardend to maintain frictional contact with said contactor wire but allowsaid sensor element to move with respect to said arm in response tochange in the vertical profile of the contactor wire as the pantographtravels therealong, and d. detecting means responsive to the movement ofsaid sensor element with respect to said support arm to activate saidadjusting means.
 7. A pantograph arrangement as set forth in claim 1wherein said at least one airfoil element is secured to said frame and,further, wherein said frame moves up and down with the collecting shoewhen said airfoil element is adjusted in response to said sensing means.8. A pantograph arrangement as set forth in claim 7 wherein said airfoilelement comprises a wing symmetrically mounted on an axis transverse tothe direction of travel, said wing being pivotable on said axis toselectively provide negative and positive aerodynamic lift in either oftwo opposite directions of travel.
 9. A pantograph arrangement as setforth in claim 8 wherein said wing includes a biasing flap attached toone side thereof and extending substantially normally therefrom, wherebyas the pantograph travels in either of said two opposite directions,said biasing flap tends to pivot said airfoil element or its axis in adirection such that its leading edge is biased towards the side of theairfoil element to which said biasing flap is attached.
 10. A pantographarrangement as set forth in claim 9 wherein said adjusting meansincludes a control flap pivotally attached to said pantograph on an axistransverse to the direction of travel, said control flap being larger incross section than said biasing flap and linked to said airfoil elementin such a manner as to apply a torque thereto opposing that exerted bysaid biasing flap.
 11. A pantograph arrangement as set forth in claim 7wherein said sensing means comprises a mechanical linkage between thecollecting shoe and the frame and further wherein the displacement ofthe shoe with respect to the frame is indicative of the pressure betweenthe shoe and the overhead wire.
 12. A pantograph arrangement as setforth in claim 7 wherein said sensing means comprises: a. a supportmeans secured to and extending from the pantograph frame in thedirection of vehicle travel; b. sensor element adjustably secured tosaid support arm at a point displaced from said collector shoe andextending upwardly to impinge on said contactor wire; c. biasing meansfor urging said upward end to maintain frictional contact with saidcontactor wire but allow said sensor to move with respect to said arm inresponse to change in the vertical profile of the contactor wire as thepantograph travels therealong; and d. detecting means responsive to themovement of said sensor element with respect to support arm to activatesaid adjusting means.